DE102022112321A1 - Method for producing a pressure vessel - Google Patents

Abstract

The invention relates to a method for producing a pressure vessel (1) for storing gaseous fuels, in particular for a motor vehicle, comprising the steps: providing a support tube (2), providing a barrier tube (3) which has an outer diameter (31). is smaller than an inner diameter (22) of the support tube (2), arranging the barrier tube (3) within the support tube (2), and deforming the support tube (2) such that an inner surface (22a) of the support tube (2) is on an outer surface (31a) of the barrier tube (3) rests to produce a double tube (4).

Description

The invention relates to a method for producing a pressure vessel for storing gaseous fuels, in particular for a motor vehicle, and to such a pressure vessel.

Pressure containers for storing fuels are known from the prior art. Storage is often carried out under high pressure. Particularly when storing hydrogen, complex and expensive measures to avoid or at least reduce diffusion and hydrogen embrittlement are required due to the high diffusivity of hydrogen and the tendency of materials in contact with the hydrogen to become brittle with hydrogen. For pressure vessels made of metal, for example steel, a special barrier layer is applied to the inside of the vessel wall. In DE 10 2020 107 562 A1 For example, it is disclosed that a barrier layer made of copper or a copper alloy is applied to the inside of the metal layer of the pressure vessel wall. The application of such barrier layers usually involves a lot of effort and comparatively high costs.

It is therefore the object of the invention to provide a method for producing a pressure vessel that can be carried out simply and cost-effectively and is particularly suitable for producing pressure vessels for storing highly diffusive substances. A further object of the invention is to provide a pressure vessel which has a simple and cost-effective structure and which allows reliable, efficient storage of fuels with high diffusivity.

This problem is solved by a method with the features of claim 1, and by a pressure vessel with the features of claim 14. The subclaims show preferred developments of the invention.

• - Bereitstellen eines Stützrohres,
• - Bereitstellen eines Sperrrohres, dass ein Außendurchmesser aufweist, der kleiner als ein Innendurchmesser des Stützrohres ist,
• - Anordnen des Sperrrohres innerhalb des Stützrohres, und
• - Verformen des Stützrohres derart, dass eine Innenfläche des Stützrohres an einer Außenfläche des Sperrrohres anliegt, zum Herstellen eines Doppelrohres.

The method according to the invention with the features of claim 1 offers the advantage that a pressure vessel can be produced particularly easily and inexpensively. The production can be carried out using simple tools and machines, and comparatively cheap and easily available materials can be used. This is achieved according to the invention by a method which comprises the steps:

• - Providing a support tube,
• - Providing a barrier tube that has an outside diameter that is smaller than an inside diameter of the support tube,
• - Arranging the barrier tube within the support tube, and
• - Deforming the support tube in such a way that an inner surface of the support tube rests on an outer surface of the barrier tube to produce a double tube.

In other words, two separate tubes are provided and pushed into one another, for example arranged coaxially to one another. Subsequently, in particular exclusively, the outer support tube is deformed, at least until it rests on the inner barrier tube, so that the two tubes form a common double tube. Advantageously, a comparatively low counter pressure can be generated by means of an internal mandrel in order to maintain the internal geometry as accurately as possible.

The support tube is preferably designed to provide mechanical stability of the pressure vessel, in particular to absorb the mechanical load resulting from filling the pressure vessel with a fuel under high pressure. The barrier tube is preferably designed to ensure that the pressure vessel is sealed and/or to prevent contact between the support tube and a fuel that can be filled into the pressure vessel. The barrier tube is particularly preferably designed to reduce the diffusion of fuel to the outside of the pressure vessel to a minimum.

The method therefore offers the advantage that a pressure vessel with optimal properties for the reliable and efficient storage of highly diffusive gaseous fuels can be produced in a particularly simple and cost-effective manner. In particular, it is particularly advantageous to provide pressure vessels for storing hydrogen as fuel, which, on the one hand, can be provided with a particularly low permeability for the hydrogen, and which, on the other hand, offer the possibility of minimizing hydrogen embrittlement by appropriately selecting the materials of the barrier tube and support tube.

Another advantage of the method is that the deformation of the support tube can take place as a radial compression of the support tube, i.e. pressure forming or pressing. This means that the pressure vessel can be manufactured using simple and cost-effective machines and forming processes.

The method preferably further comprises the step which is carried out before the support tube is deformed: joint compression of the support tube and barrier tube in the radial direction at a compression section. The compression section is preferably one into the other at an axial end of the two pushed pipes arranged. In particular, the barrier tube and support tube are deformed in such a way that after deformation the outer diameter of the support tube is smaller than the outer diameter of the barrier tube before deformation. As a result, the two tubes are fixed to one another at the compression section, so that relative axial displacement is prevented. This means that the subsequent deformation of the support tube can be carried out in a particularly targeted and precise manner in order to achieve the desired geometry.

Particularly preferably, the method further comprises the step which is carried out after the support tube has been deformed: producing at least one dome-shaped end region by deforming a partial region of the double tube, preferably by means of hot spin forming. A dome-shaped or essentially spherical taper of a part of the double tube is viewed as a dome-shaped end region. For example, a nozzle can additionally, preferably simultaneously, be formed adjacent to the dome-shaped area. For example, such a connector can be used to connect the pressure vessel. In particular, the dome-shaped area is thus created by reducing the diameter of a portion of the double tube by pressing in the radial direction. This means that the pressure container can be manufactured in a particularly simple and cost-effective manner, since such pressing can be carried out, for example, with little machine effort and in a particularly time-efficient manner.

The deformation of the support tube is preferably carried out by simultaneously radially compressing and axially stretching the support tube. This allows a simple and targeted reshaping of the support tube to achieve the desired geometry. Furthermore, gentle forming can be carried out in order to be able to provide optimal material properties of the pressure vessel.

Preferably, the method further comprises the step of: separating the double pipe into a plurality of double pipe pieces in order to produce a plurality of pressure vessels. This means that the production of the double tube by deforming the support tube until its inner surface rests on the outside of the barrier tube, and preferably the joint compression of the support tube and barrier tube, takes place on exactly one double tube, from which several separate pressure vessels can then be produced. This makes it possible to provide a particularly efficient and cost-effective manufacturing process.

• - Kohlenstoff bis 0,10 Gew.-%, vorzugsweise 0,01 Gew.-% bis 0,03 Gew.-%;
• - Silizium bis 1,0 Gew.-%, vorzugsweise 0,01 Gew.-% bis 0,80 Gew.-%;
• - Mangan bis 2,0 Gew.-%, vorzugsweise 0,3 Gew.-% bis 1,5 Gew.-%;
• - Chrom bis 20 Gew.-%, vorzugsweise 16,5 Gew.-% bis 18,5 Gew.-%;
• - Molybdän bis 3,0 Gew.-%, vorzugsweise 2,0 Gew.-% bis 2,5 Gew.-%;
• - Nickel bis 15 Gew.-%, vorzugsweise 10,0 Gew.-% bis 13,0 Gew.-%;
• - Titan bis 0,2 Gew.-% vorzugsweise 0,02 Gew.-% bis 0,1 Gew.-%;
• - Vanadium bis 0,2 Gew.-%;
• - Aluminium bis 0,2 Gew.-%, vorzugsweise 0,02 Gew.-% bis 0,07 Gew.-%;
• - Stickstoff bis 0,15 Gew.-%, vorzugsweise bis 0,11 Gew.-%;
• - Schwefel max. 0,015 Gew.-%, vorzugsweise max. 0,008 Gew.-%;
• - Phosphor max. 0,045 Gew.-%, vorzugsweise max. 0,025 Gew.-%.

The barrier tube is preferably made of an austenitic steel. Such a barrier tube offers the advantage that a particularly low diffusivity for hydrogen can be provided. In addition, such a barrier tube has a low susceptibility to hydrogen embrittlement. The austenitic steel preferably has at least one of the following components in the appropriate concentration:

• - Carbon up to 0.10% by weight, preferably 0.01% by weight to 0.03% by weight;
• - Silicon up to 1.0% by weight, preferably 0.01% by weight to 0.80% by weight;
• - Manganese up to 2.0% by weight, preferably 0.3% by weight to 1.5% by weight;
• - Chromium up to 20% by weight, preferably 16.5% by weight to 18.5% by weight;
• - Molybdenum up to 3.0% by weight, preferably 2.0% by weight to 2.5% by weight;
• - Nickel up to 15% by weight, preferably 10.0% by weight to 13.0% by weight;
• - Titanium up to 0.2% by weight, preferably 0.02% by weight to 0.1% by weight;
• - vanadium up to 0.2% by weight;
• - Aluminum up to 0.2% by weight, preferably 0.02% by weight to 0.07% by weight;
• - Nitrogen up to 0.15% by weight, preferably up to 0.11% by weight;
• - Sulfur max. 0.015% by weight, preferably max. 0.008% by weight;
• - Phosphorus max. 0.045% by weight, preferably max. 0.025% by weight.

The austenitic steel particularly preferably has all of these components mentioned in the respective concentration, with the remainder preferably consisting of iron and impurities.

• - Kohlenstoff bis 0,45 Gew.-%, vorzugsweise 0,36 Gew.-% bis 0,43 Gew.-%;
• - Silizium bis 2,0 Gew.-%, vorzugsweise 1,40 Gew.-% bis 1,90 Gew.-%, besonders bevorzugt 1,60 Gew.-% bis 1,75 Gew.-%;
• - Mangan bis 1,0 Gew.-%, vorzugsweise 0,40 Gew.-% bis 0,90 Gew.-%, besonders bevorzugt 0,75 Gew.-% bis 0,85 Gew.-%;
• - Chrom bis 1,0 Gew.-%, vorzugsweise 0,60 Gew.-% bis 0,90 Gew.-%, besonders bevorzugt 0,75 Gew.-% bis 0,85 Gew.-%;
• - Molybdän bis 0,50 Gew.-%, vorzugsweise 0,35 Gew.-% bis 0,45 Gew.-%;
• - Nickel bis 2,0 Gew.-%, vorzugsweise 1,20 Gew.-% bis 1,90 Gew.-%, besonders bevorzugt 1,70 Gew.-% bis 1,80 Gew.-%;
• - Titan bis 0,2 Gew.-%;
• - Vanadium bis 0,2 Gew.-%, vorzugsweise 0,05 Gew.-% bis 0,15 Gew.-%, besonders bevorzugt 0,070 Gew.-% bis 0,090 Gew.-%;
• - Aluminium bis 0,2 Gew.-%, vorzugsweise 0,01 Gew.-% bis 0,04 Gew.-%;
• - Stickstoff bis 0,15 Gew.-%, vorzugsweise bis 0,10 Gew.-%;
• - Schwefel max. 0,015 Gew.-%, vorzugsweise max. 0,008 Gew.-%;
• - Phosphor max. 0,025 Gew.-%, vorzugsweise max. 0,015 Gew.-%.

More preferably, the support tube is formed from a martensitic steel. This achieves the advantage that a particularly mechanically stable pressure vessel can be provided. In addition, the material costs for the pressure vessel can be reduced. The martensitic steel preferably has at least one of the following components in the appropriate concentration:

• - Carbon up to 0.45% by weight, preferably 0.36% by weight to 0.43% by weight;
• - Silicon up to 2.0% by weight, preferably 1.40% by weight to 1.90% by weight, particularly preferably 1.60% by weight to 1.75% by weight;
• - Manganese up to 1.0% by weight, preferably 0.40% by weight to 0.90% by weight, particularly preferably 0.75% by weight to 0.85% by weight;
• - Chromium up to 1.0% by weight, preferably 0.60% by weight to 0.90% by weight, particularly preferably 0.75% by weight to 0.85% by weight;
• - Molybdenum up to 0.50% by weight, preferably 0.35% by weight to 0.45% by weight;
• - Nickel up to 2.0% by weight, preferably 1.20% by weight to 1.90% by weight, particularly preferably 1.70% by weight to 1.80% by weight;
• - Titanium up to 0.2% by weight;
• - Vanadium up to 0.2% by weight, preferably 0.05% by weight to 0.15% by weight, particularly preferably 0.070% by weight to 0.090% by weight;
• - Aluminum up to 0.2% by weight, preferably 0.01% by weight to 0.04% by weight;
• - Nitrogen up to 0.15% by weight, preferably up to 0.10% by weight;
• - Sulfur max. 0.015% by weight, preferably max. 0.008% by weight;
• - Phosphorus max. 0.025% by weight, preferably max. 0.015% by weight.

The martensitic steel particularly preferably has all of these components mentioned in the respective concentration, with the remainder preferably consisting of iron and impurities.

The barrier tube and the support tube are preferably formed from materials which have essentially the same coefficient of thermal expansion. This makes it possible to ensure a similar thermal expansion of these two components of the pressure vessel, whereby, for example, gaps and/or undesirable tensions can be avoided. Alternatively, the barrier tube is preferably formed from a material that has a greater coefficient of thermal expansion than a material of the support tube. This causes, for example, that the barrier tube expands more than the support tube when heated. This causes a press connection between the two pipes to occur when the double pipe and/or the pressure vessel heats up, for example instead of loosening or forming a gap between the two pipes.

Preferably, a first wall thickness of the barrier tube is a maximum of 80%, preferably a maximum of 50%, particularly preferably a maximum of 30% of a second wall thickness of the support tube. This means that the barrier tube is thinner-walled compared to the support tube. This makes it possible to provide a particularly cost-effective pressure vessel, particularly if the barrier tube is made of an austenitic steel and the support tube is made of a martensitic steel.

More preferably, an outer diameter of the barrier tube is a maximum of 95%, preferably a maximum of 80%, particularly preferably at least 60%, of the inner diameter of the support tube. Preferably, a state before the support tube is deformed is considered. In particular, there is a radial gap between the two tubes before deformation. Such a radial gap is particularly preferably at least 5 mm, preferably a maximum of 10 mm. This allows the two pipes to be pushed into one another in a particularly simple and smooth manner.

Particularly preferably, the method further comprises the step of heat treating the double tube, preferably after producing the dome-shaped end region. This allows particularly advantageous material properties, such as high strength of the pressure vessel, to be achieved.

• - Härten,
• - Abschrecken,
• - erstes Anlassen,
• - Luftabkühlung,
• - zweites Anlassen, und
• - Luftabkühlung

The heat treatment preferably includes the following steps in the order mentioned:

• - hardening,
• - Scare off,
• - first start,
• - air cooling,
• - second starting, and
• - Air cooling

Preferably, the method further comprises the step of coating the double pipe, preferably with a corrosion protection layer, in particular on an outside of the double pipe. This makes it possible to provide a particularly long-lasting pressure vessel that is resistant to external environmental influences.

Furthermore, the invention leads to a pressure vessel for storing gaseous fuels, in particular for a motor vehicle, the pressure vessel being produced by means of the method described above. The pressure vessel is therefore characterized by a simple and cost-effective structure, allowing high resistance to hydrogen embrittlement and diffusion of hydrogen from the pressure vessel to the outside.

• 1 eine vereinfachte schematische Schnittansicht eines Druckbehälters gemäß einem bevorzugten Ausführungsbeispiel der Erfindung,
• 2 einen Schritt eines Herstellungsverfahrens des Druckbehälters der 1, und
• 3 einen weiteren Schritt des Herstellungsverfahrens des Druckbehälters der 1.

Further details, advantages and features of the present invention emerge from the following description of exemplary embodiments based on the drawing. It shows:

• 1 a simplified schematic sectional view of a pressure vessel according to a preferred embodiment of the invention,
• 2 a step of a manufacturing process of the pressure vessel 1 , and
• 3 a further step in the manufacturing process of the pressure vessel 1 .

Below is with reference to the 1 until 3 a container 1 and a method for producing the pressure vessel according to a preferred embodiment of the invention are described. In the figures, functional components are always marked with the same reference numbers.

The pressure vessel 1 is intended for storing gaseous fuels, which can preferably be used as fuels for motor vehicles. In particular, the container 1 is intended for storing gaseous hydrogen under high pressure.

To produce the pressure vessel 1, a support tube 2 and a barrier tube 3 are first provided (see 2 ). The barrier tube 3 has an outer diameter 31 which is smaller than an inner diameter 22 of the support tube 2.

A first wall thickness 33 of the barrier tube 3 is smaller than a second wall thickness 23 of the support tube 2. Preferably, the first wall thickness 33 is a maximum of 50% of the second wall thickness 23.

The two tubes 2, 3 are made of steel. In detail, the barrier tube 3 is made of an austenitic steel and the support tube 2 is made of a martensitic steel.

Furthermore, the materials of the two tubes 2, 3 are selected such that the barrier tube 3 is formed from a material that has a greater coefficient of thermal expansion than a material of the support tube.

At the beginning of the manufacturing process, the barrier tube 3 is arranged within the support tube 2, for example as in the 2 shown coaxial to each other. In this configuration there is a gap 48 in the radial direction between the two tubes 2, 3.

The two tubes are then compressed together in this nested configuration. Both the support tube 2 and the barrier tube 3 are deformed in the radial direction, such that after deformation, an outer diameter 21 'of the support tube 2 after deformation is smaller than an inner diameter 32 of the barrier tube 3 before deformation (compare 2 and 3 ). The compression of the support tube 2 and barrier tube 3 only takes place within a compression section 40, which lies at an axial end of the two tubes 2, 3. As a result, the barrier tube 3 and the support tube 2 are held together in an axially immovable manner by means of the compression section 40.

The support tube 2 is then deformed. The support tube 2 is simultaneously compressed in the radial direction (compare arrows B in 2 ) and stretched in the axial direction (compare arrows C 2 ). The support tube 2 is deformed until it rests on an outer surface 31a of the barrier tube 3, preferably in such a way that there is a press connection between the support tube 2 and the barrier tube 3. A double tube 4 is thus formed from the support tube 2 and the barrier tube 3. The double pipe 4 is in the 3 pictured.

The double tube 4 is then separated into several double tube pieces 41 along the axial direction. A separate pressure vessel 1 can then be produced from each of these double pipe pieces 41.

To produce the pressure vessel 1, a dome-shaped end region 45 and a connection region 46 are then produced at each axial end of the double pipe section 41 (see 1 ).

The dome-shaped end region 45 forms a dome-shaped taper of the inner and outer contours of the double pipe section 41, which opens into the connection region 46. The connection area 46 is designed as a straight tubular end piece of the pressure vessel 1.

To produce the dome-shaped end region 45 and the connection region 46, the corresponding double pipe piece 41 is partially deformed radially inwards by a pressing forming process, preferably hot spin forming.

An internal thread 47 can then be formed on each of the connection areas 46 on its inner circumference, by means of which, for example, a connection element 49 can be connected to the pressure vessel 1. By means of the connection element 49, for example, an inner cavity 5 of the pressure vessel, in which the gaseous fuel can be stored under pressure, can be brought into fluid communication with a line via which the gaseous fuels can be transported further, for example to a consumer. At the connection Element 49 opposite connection area 46, for example, a closure element can be provided in order to close the cavity 5 at this end of the pressure vessel 1 in a fluid-tight manner.

Reference symbol list

1

pressure vessel

2

Support tube

3

Barrier tube

4

Double pipe

5

cavity

21

Outer diameter support tube

22

Inner diameter support tube

22a

Inner surface support tube

23

second wall thickness support tube

31

Outer diameter barrier tube

32

Inner diameter barrier tube

32a

Outer surface barrier pipe

33

first wall thickness barrier pipe

40

compression section

41

Double pipe pieces

45

dome-shaped end area

46

Connection area

47

inner thread

48

gap

49

Connection element

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102020107562 A1 [0002]

Claims (14)

Method for producing a pressure vessel (1) for storing gaseous fuels, in particular for a motor vehicle, comprising the steps: - Providing a support tube (2), - Providing a barrier tube (3) which has an outer diameter (31) which is smaller than an inner diameter (22) of the support tube (2), - Arranging the barrier tube (3) within the support tube (2), and - Deforming the support tube (2) in such a way that an inner surface (22a) of the support tube (2) rests on an outer surface (31a) of the barrier tube (3) to produce a double tube (4). Procedure according to Claim 1 , further comprising the step before deforming the support tube (2): - joint compression of the support tube (2) and barrier tube (3) in the radial direction on a compression section (40), which is in particular at an axial end of the two tubes (2, 3 ) lies. Method according to one of the preceding claims, further comprising the step after deforming the support tube (2): - Producing at least one dome-shaped end region (45) by deforming the double tube (4), in particular by means of hot spin forming. Method according to one of the preceding claims, wherein the support tube (2) is deformed by simultaneous radial compression and axial stretching. Method according to one of the preceding claims, further comprising the step: - Separating the double pipe (4) into several double pipe pieces (41) to produce several pressure vessels. Method according to one of the preceding claims, wherein the barrier tube (3) is formed from an austenitic steel. Method according to one of the preceding claims, wherein the support tube (2) is formed from a martensitic steel. Method according to one of the preceding claims, - wherein the barrier tube (3) and the support tube (2) are formed from materials with essentially the same coefficient of thermal expansion, or - wherein the barrier tube (3) is formed from a material that has a greater coefficient of thermal expansion than a material of the support tube (2). Method according to one of the preceding claims, wherein a first wall thickness (33) of the barrier tube (3) is a maximum of 80%, preferably a maximum of 50%, particularly preferably a maximum of 30%, of a second wall thickness (23) of the support tube (2). Method according to one of the preceding claims, wherein the outer diameter (31) of the barrier tube (3) is a maximum of 95%, preferably a maximum of 80%, particularly preferably at least 60%, of the inner diameter (22) of the support tube (2). Method according to one of the preceding claims, further comprising the step: - Heat treatment of the double tube (4). Procedure according to Claim 11 , where the heat treatment includes the sequential steps: hardening, quenching, first tempering, air cooling, second tempering, air cooling. Method according to one of the preceding claims, further comprising the step: - Coating the double pipe (4), in particular with a corrosion protection layer. Pressure vessel (1) for storing gaseous fuels, in particular for a motor vehicle, produced by a method according to one of the preceding claims.

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